Differential temperature push bending method and device for tube with small bending radius

Abstract

Disclosed are differential temperature push bending method and device for tube with small bending radius, the device comprising: a push bending die, core, fillers and pushers, wherein the core and the fillers are both arranged in a bending chamber of the push bending die, an inlet and an outlet end of the push bending die are respectively provided with a front guiding sleeve and a rear guiding sleeve, the pusher in the front guiding sleeve abuts against a plurality of fillers, and the pusher in the rear guide sleeve abuts against the core. A heat rod is provided at an outer end of the bending chamber. The present disclosure adopts differential temperature type push bending, flow performance of the tube blank at the outer corner of the die can be improved, and the material can be timely fed to prevent excessive stretching and thinning of the outer material.

What is claimed is: 
     
       1. A method for achieving differential temperature push bending for tube with small bending radius using a device comprising: a push bending die, cores, a filler and pushers, wherein the cores and the filler are both arranged in a curved bending chamber of the push bending die, an inlet of the push bending die is provided with a front guiding sleeve, an outlet end of the push bending die is provided with a rear guiding sleeve, an end of at an outer side of the bending chamber of the push bending die is provided with a heating rod, an end at an inner side of the curved bending chamber of the push bending die is provided with a cooling water channel, a first thermocouple is disposed near the heating rod, a second thermocouple is disposed near the cooling water channel, a first pusher in the front guiding sleeve abuts against the filler, and a second pusher in the rear guide sleeve abuts against the cores, the method comprising the steps of:
 step 1: blanking a tube blank, a length of the tube blank being larger than πD, chamfering a front end at a curved inner side of the tube blank at an oblique angle of 30° to 45°, chamfering a rear end of the curved inner side of the tube blank that is in contact with the first pusher at an oblique angle of 45° to 60°, then cutting and flattening a slope of a pushed end of the tube blank along a center line of the tube blank, and finally deburring two ends of the tube blank and cleaning the inner and outer sides of the tube blank; 
 step 2: applying a lubricant to the tube blank, the lubricant being a high temperature resistant lubricant; 
 step 3: filling the filler having a hardness of 80 to 85 A Shore hardness inside the pushed end of the tube blank, the filler being rubber cylindrical blocks, each of the rubber cylindrical blocks having a diameter that is 2 mm smaller than an inner diameter of the tube blank; 
 step 4: energizing the heating rod, the heating rod heating the push bending die to a set temperature and keeping a temperature after heating constant, the set temperature being 200-400° C., and a variance of the temperature after heating being less than 2° C.; a deformation temperature of the tube blank being increased, so that a plasticity of an outer tube structure during a bending process is improved; 
 step 5: injecting cooling water into the cooling water channel provided in the push bending die, heat inside the push bending die being taken away by a flow of the cooling water to lower a temperature inside the push bending die, and an initial water temperature of the cooling water being room temperature; 
 step 6: after the first thermocouple and the second thermocouple detecting a differential temperature between an inner side and an outer side of the push bending die is 100-300° C., placing the tube blank in the push bending die, ensuring that the pushers and the cores are fixed in an initial position, increasing a thrust on a top of the core, providing an internal pressure in the tube blank by the fillers, forcing a material of the tube blank to flow towards a front groove, the tube blank moving forward at a constant speed by the thrust of the pusher, while the cores moving backwards, thus gradually completing the bending of tube blank with small bending radius for the tube blank; 
 step 7: after the bending being completed, removing the lubricant on a surface of the tube blank. 
 
     
     
       2. The method according to  claim 1 , wherein in the step 3, whether to use fluororubber or perfluoroether rubber is determined by the bending temperature of the tube blank. 
     
     
       3. The method according to  claim 1 , wherein in the step 6, a moving distance of the pushers is πD.